This application is a continuation based on PCT International Application No. PCT/JP00/09374, filed on Dec. 20, 2000, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.
The present invention relates generally to heat radiator mechanisms, and more particularly to a heat radiator mechanism for radiating the heat from an exoergic circuit element or exoergic component mounted in an electronic apparatus. The present invention is suitable, for example, for a heat sink that radiates the heat from various exoergic circuit elements on a printed board in a personal computer (xe2x80x9cPCxe2x80x9d).
PCs are broadly available in the market as a typical information processor. A motherboard or main board in the PC is mounted with various circuit components such as a CPU socket, a variety of memory (sockets), a chipset, an expansion slot, and a BIOS ROM, and directly affects performance and functions of the PC.
Recent PCs tend to include an increased number of exoergic components and to generate more calorific values from them as various circuit components mounted on the motherboard provide higher speed and performance. The heat destabilizes operations of circuit components, and finally lowers the operational performance of a PC. Therefore, the PC provides the motherboard with a heat radiator mechanism called a heat sink in order to thermally protect the exoergic components and other circuit components mounted directly or via a socket or the like on the motherboard.
A description will be given of a conventional typical heat sink 500 with reference to FIGS. 18 and 19, and another conventional heat sink 600 with reference to FIGS. 20 and 21. Here, FIGS. 18 and 19 are schematic side and plane views of the heat sink 500. FIGS. 20 and 21 are schematic side and plane views of the heat sink 600. The heat sink typically includes plural cooling or radiating fins (or sometimes called xe2x80x9cfin assemblyxe2x80x9d) made of a material having high heat conductivity, and cools exoergic components by forced or spontaneous air cooling. The heat sink 500 includes a base 510 placed on an exoergic component (not shown) mounted on a motherboard (not shown), and a radiating part 520 that includes plural parallel plate-shaped fins 522 that extend from the base 510 perpendicular to the motherboard or in a direction Z in FIG. 18. The head sink 600 includes a base 610 placed on an exoergic component (not shown) mounted on a motherboard (not shown), and a radiating part 620 that includes plural pinholder-shaped fins 522 that extend from the base 610 perpendicular to the motherboard or in a direction Z in FIG. 20.
A fan-cum-heat sink that includes a fan has been proposed to enhance a cooling effect of the heat sink. The fan-cum-heat sink provides forced-air cooling to the heat sink with air currents produced by a fan.
A higher speed and more functions of various circuit elements have drastically increased the calorific values from the circuit elements, and required the heat sink to have higher heat radiation performance. Conceivably, this request would be met by increasing surface areas of the radiating parts 520 and 620 in the conventional heat sinks 500 and 600.
A conceivable way of increasing the surface area of the radiating part 520 or 620 is to narrow an interval or pitch between fins 522 or 622 and increase the number of fins 522 or 622 per unit area and/or to thicken each fin 522 or 622. Both of these methods eventually narrow a pitch, and reduce the air convection that passes between the fins 522 or 622, lowering the cooling efficiency at center parts of the bases 510 and 610 (this condition is sometimes called xe2x80x9cincreased pressure lossxe2x80x9d in this application).
It is also conceivable to extend the height of the fins 522 or 622 in the height direction or direction Z to increase the surface area of the radiating part 520 or 620. However, the fin 522 or 622 has such a temperature gradient in the direction Z that the excessively high fin 522 or 622 has lowered heat exchanger effectiveness and cooling efficiency on its top. In order to rectify this shortcoming, it is also conceivable to replace a material of the fin 522 or 622 with a material having high heat conductivity for the reduced temperature gradient in the height direction or the direction Z. For example, it is conceivable to replace aluminum, typically used for the fins 522 and pins 622, which has heat conductivity of 203 W/mxc2x7K with copper that has heat conductivity of 372 W/mxc2x7K. However, copper needs anti-oxidant coating, and complexes the manufacture process. In addition, copper is heavier than aluminum and an undesirable material to be attached to a top of the component. The length in the direction Z is restricted by the mounting space limitation in the PC.
It is also conceivable to attach a fan to a heat sink to enhance the heat conductivity, but this deteriorates energy saving aspect and economical efficiency of the heat sink.
Thus, some parameters should be considered which include the pressure loss instead of merely increasing the surface area of the fin in order to enhance the heat radiation efficiency in a heat sink.
Accordingly, it is a general object of the present invention to provide a novel and useful heat radiator mechanism and electronic apparatus having the same in which the above disadvantages are eliminated.
Another exemplified and more specific object of the present invention is to provide a heat radiator mechanism and electronic apparatus having the same, which comparatively inexpensively enhance the entire heat radiation efficiency taking into account some parameters including pressure loss.
A heat sink of one embodiment according to the present invention includes a heat receiving part for receiving heat from the outside, a first radiating part, connected to the heat receiving part, which forms a first air channel, and radiates the heat from the heat receiving part using air that passes through the first air channel, and a second radiating part, located apart from the heat receiving part and connected to the first radiating part, the second radiating part forming a second air channel which the air that has passed the first air channel enters, the second air channel being narrower than the first air channel, the second radiating part radiating the heat from the first radiating part. This heat sink may radiate the heat from the heat receiving part using the first and second radiating parts. The first radiating part forms the first air channel, and radiates the heat as a result of that the air passes through the first air channel. The air that has passed through the first air channel may enter the second air channel of the second radiating part narrower than the first air channel, and the second radiating part may radiate the heat using the air convection. The second radiating part is spaced from the first radiating part by a predetermined distance that contributes to definition of the first air channel at the first radiating part. The first radiating part of the heat sink includes, for example, plural fins, and the second radiating part is provided between two fins, thereby maintaining the second air channel. The sufficiently large second air channel may be maintained by providing the second radiating part with second fin thinner than the first fin. Moreover, this heat sink forms a surface area of the second radiating part larger than that of the first radiating part, maintains the sufficiently wide heat radiation area and enhances the heat radiation effect. The heat sink includes a side plate that encloses the second radiating part and defines an air channel, so as to assist the second radiating part in radiating the heat. The second radiating part includes a first part near a center, and a second part, located outside the first part, which has a larger surface area than the first part. A wide heat radiation area may be obtained by forming the first part larger than the second part that promotes the air convection. A similar operation may be obtained by making the second part longer than the first part in the height direction. Alternatively, the first part longer than the second part in the height direction would promote the air convection at the first part and enhance the heat radiation efficiency. The convection at the second radiating part may be promoted and the heat radiation efficiency may be promoted by forming a notch in the thin plate, and raising the notch to form a raised piece as a bent projection and disturb the airflow. This notch may connect adjacent second air channels. The increased number of pillar parts and a shape of the pillar part would promote the air convection and enhance the heat radiation efficiency.
An electronic apparatus of another embodiment according to the present invention includes a printed board mounted with an exoergic component, and a heat sink, provided on the printed board, which cools the exoergic component, wherein the heat sink includes a heat receiving part for receiving heat from the outside, a first radiating part, connected to the heat receiving part, which forms a first air channel, and radiates the heat from the heat receiving part using air that passes through the first air channel, and a second radiating part, located apart from the heat receiving part and connected to the first radiating part, the second radiating part forming a second air channel which the air that has passed the first air channel enters, the second air channel being narrower than the first air channel, the second radiating part radiating the heat from the first radiating part. This electronic apparatus has the above heat sink, and exhibits similar operations to those of the heat sink.
Other objects and further features of the present invention will become readily apparent from the following description of the embodiments with reference to accompanying drawings.